Skipping Fluxbox Tabbed windows

[lab156]

Fluxbox has tabbed windows, in which several windows can be stacked on top of each other and share geometry and position.
By default, alttab shows and cycles around all windows in the current workspace. Is there a way to make alttab skip through the windows that are tabbed together and only show the independent windows. This is fluxbox's default behavior but alttab has several other features that I like.

[sagb]

This is probably a useful feature. I will try to find time to implement it.